1. Field of the Invention
This invention relates to brake mechanisms for tape cassettes, for example magnetic tape cassettes for recording video and/or audio and/or other information.
2. Description of the Prior Art
FIGS. 1 to 3 of the accompanying drawings show a previously proposed 8 mm video tape cassette that comprises a cassette housing 10 having an upper half or portion 12 and a lower half or portion 14. Reels 16, 18 are rotatably mounted on the lower housing portion 14. The reels 16, 18 have upper flanges (not shown in the drawings for the sake of clarity) and lower or bottom flanges 20, 22. The flanges 20, 22 have teeth 24, 26 formed around their outer peripheries. The lower housing portion 14 is provided with reel drive openings 28, 30 to enable the hubs 32, 34 of the reels 16, 18 to be engaged by reel drive means of a recording and/or reproducing apparatus (not shown). A magnetic tape 36, wound on the reels 16, 18, is entrained around guide portions 38, 40 of the lower housing portion 14 to follow the path shown in FIG. 1. When the cassette is installed in the recording and/or reproducing apparatus, a front lid or cover 42 hingedly fitted to the upper housing portion 12 is pivoted upwardly of the cassette housing 10 to allow access to the run of the tape 36 extending between the guide portions 38, 40 by tape engagement means (not shown) that can enter the cassette housing 10 through an opening 44 in the lower housing portion 14. The upper housing portion 12 is provided with an opening 46 covered by a hingedly mounted member 48.
When the cassette is not in an operative position in the recording and/or reproducing apparatus, the reels 16, 18 are locked in position by a brake or lock mechanism which includes a reel stopper 50 mounted for sliding movement within a guideway 52. The guideway 52 is defined by a bottom wall 14a and a rear wall 14b of the lower housing portion 14 and by ribs or guide walls 54, 56. The axis of the guideway 52 extends between the reels 16, 18 so that the reel stopper is slidable in a direction extending between the reels, 16, 18. As can best be seen from FIG. 2, the ribs or guide walls 54, 56, together with ribs 57, 59, can be formed integrally with the lower housing portion 14.
A coil spring 60, which is secured by members 61 to the base of the guideway 52 (i.e. the lower end of the guideway as viewed in FIG. 2), acts between the base of the guideway and the reel stopper 50 so as to bias the reel stopper toward a locking position, shown by solid lines in FIG. 2, in which the reel stopper is adjacent the mouth of the guideway (i.e. the upper end of the guideway as viewed in FIG. 2), and in which the brake mechanism locks the reels 16, 18 in position. The locking position is defined by a tapered end portion of a base block or member 62 of the reel stopper abutting against the free ends or tips 54a, 56a of the guide walls 54, 56, which are correspondingly inclined inwardly towards one another.
The reel stopper 50 includes a pair of stopper members or arms 64, 66 fitted to the base block 62. Each stopper member 64, 66 is in the form of a thin, resiliently deformable (flexible) blade or leaf and is formed simultaneously with the base block 62 by resin injection molding. The stopper members 64, 66 are configured and oriented with precision so that, when the reel stopper 50 is in the above-mentioned locking position, the tips or free ends 64a, 66a of the stopper members engage the teeth 24, 26 of the lower flanges 20, 22 of the reels 16, 18, as shown by the upper solid line positions of the stopper members in FIG. 2, to lock the reels in position.
As can be seen from FIG. 3, the base block 62 of the reel stopper 50 is provided with a hollow 68 which is accessible by way of a slot or cutout 70 in the bottom wall 14a of the lower housing portion 14. When the cassette is installed in the recording and/or reproducing apparatus and the tape 36 is to be released for transport, a lock release pin 72 of the apparatus is inserted into the hollow 68 via the slot 70. The pin 72 is moved in the direction of an arrow b (FIGS. 2 and 3) and engages a wall 74 of the hollow 68 in the base block. As the pin 72 moves in the direction of the arrow b from the position shown in FIG. 3 in full lines to that shown by chain-dotted lines, the base block 62 is correspondingly moved away from its locking position (shown by full lines in FIG. 2) toward the base of the guideway 52, and against the action of the coil spring 60, to a release position shown by chain-dotted lines in FIG. 2. During the course of this movement, the stopper members 64, 66 (which, of course, move together with the base block 62) are resiliently deformed toward one another by virtue of their engaging tips or end portions 54a, 56a of the ribs or guide walls 54, 56. The relative orientation of the stopper members 64, 66 thus changes from the splayed apart orientation shown by the upper solid lines in FIG. 2 to the somewhat relatively inwardly bowed configuration shown by the lower solid lines in FIG. 2. During the release movement, whose stroke is shown at l in FIG. 2, the tips or free ends 64a, 66a of the stopper members 64, 66 come out of engagement with the teeth 24, 26 of the lower flanges 20, 22 of the reels 16, 18 whereby the reels are unlocked and the tape 36 can be transported for recording and/or reproduction.
When the reels 16, 18 are again to be locked, the lock release pin 72 is moved in the direction represented by an arrow a in FIGS. 2 and 3, as a result of which the reel stopper 50 is urged by the coil spring 60 back into its locking position in which the tips or free ends 64a, 66a of the stopper members 64, 66 engage the teeth 24, 26 of the lower flanges 20, 22 of the reels 16, 18 to lock the reels in position.
The above-described brake or lock mechanism is subject to two disadvantages. First, since the stopper members 64, 66 are quite thin, if one or both of the reels 16, 18 is forcibly rotated, when locked in position, in directions represented by arrows c and d in FIG. 2, the stopper members can become bent, as shown by chain-dotted lines in FIG. 2. In the worst case, the stopper members 64, 66 can even be broken. Second, as the reel stopper 50 slides over the limited stroke represented by the arrow l in FIG. 2 to unlock the reels 16, 18, in order to guarantee complete release of the stopper members from the teeth 24, 26 the stopper members are forced to flex toward one another, as explained above, by engagement of the stopper members with the tips or free ends 54a, 56a of the ribs 54, 56. Since, as noted above, the stopper members 54, 56 are thin, they tend to become deformed to such an extent that their opening angle (i.e. their relative orientation) departs from the precise value determined in manufacture by the injection molding operation, whereby the reel stopper may eventually fail to function to lock the reels 16, 18.